DTC B1780: Front Occupant Classification Sensor LH Circuit Malfunction: Procedure

1. Turn the power switch off.
2. Disconnect the cable from the negative (-) battery terminal.
3. Check that the connectors are properly connected to the occupant classification ECU and front occupant classification sensor LH.

   OK

   The connectors are properly connected.

   HINT: 

   If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.

4. Disconnect the connectors from the occupant classification ECU and front occupant classification sensor LH.
5. Check that the terminals of connectors are not damaged.

   OK

   The terminals are not deformed or damaged.

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Connect the cable to the negative (-) battery terminal.
   Fig 1: Identifying Front Seat Wire RH (Short To B+)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Turn the power switch on (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   W2-1 (SGD1) - Body ground	Power switch on (IG)	Below 1 V
   W2-7 (SIG1) - Body ground	Power switch on (IG)	Below 1 V
   W2-11 (SVC1) - Body ground	Power switch on (IG)	Below 1 V

   TEXT IN ILLUSTRATION
   
   

   *1	Front Occupant Classification Sensor LH
   *2	Occupant Classification ECU
   *3	Front Seat Wire RH
   *4	Front view of wire harness connector (to Occupant Classification ECU)
   *5	Connector B

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Turn the power switch off.
   Fig 2: Identifying Front Seat Wire RH (Open)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the cable from the negative (-) battery terminal.
3. Using SST, connect terminals 1 (SVC1) and 3 (SGD1), and connect terminals 2 (SIG1) and 3 (SGD1) of connector C.
   NOTE:

   Do not forcibly insert SST into the terminals of the connector when connecting.

   • SST: 09843-18040 
4. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   W2-7 (SIG1) - W2-1 (SGD1)	Always	Below 1 Ω
   W2-11 (SVC1) - W2-1 (SGD1)	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

   *1	Front Occupant Classification Sensor LH	*2	Occupant Classification ECU
   *3	Front Seat Wire RH	*4	Front view of wire harness connector (to Occupant Classification ECU)
   *5	Front view of wire harness connector (to Front Occupant Classification Sensor LH)	*6	Connector B
   *7	Connector C	-	-

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Disconnect SST from connector C.
   Fig 3: Identifying Front Seat Wire RH (Short To B+)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   W2-7 (SIG1) - W2-1 (SGD1)	Always	1 MΩ or higher
   W2-11 (SVC1) - W2-1 (SGD1)	Always	1 MΩ or higher
   W2-7 (SIG1) - W2-11 (SVC1)	Always	1 MΩ or higher

   TEXT IN ILLUSTRATION
   
   

   *1	Front Occupant Classification Sensor LH
   *2	Occupant Classification ECU
   *3	Front Seat Wire RH
   *4	Front view of wire harness connector (to Occupant Classification ECU)
   *5	Connector B

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Measure the resistance according to the value(s) in the table below.
   Fig 4: Identifying Front Seat Wire RH (Short To B+)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   W2-1 (SGD1) - Body ground	Always	1 MΩ or higher
   W2-7 (SIG1) - Body ground	Always	1 MΩ or higher
   W2-11 (SVC1) - Body ground	Always	1 MΩ or higher

   TEXT IN ILLUSTRATION
   
   

   *1	Front Occupant Classification Sensor LH
   *2	Occupant Classification ECU
   *3	Front Seat Wire RH
   *4	Front view of wire harness connector (to Occupant Classification ECU)
   *5	Connector B

NG → REPLACE FRONT SEAT WIRE RH 

OK: Go to next step 

1. Connect the connectors to the occupant classification ECU and front occupant classification sensor LH.
2. Connect the cable to the negative (-) battery terminal.
3. Turn the power switch on (IG).
4. Clear the DTCs stored in the occupant classification ECU. Refer to DTC CHECK / CLEAR .
5. Clear the DTCs stored in the center airbag sensor assembly. Refer to DTC CHECK / CLEAR .
6. Turn the power switch off.
7. Turn the power switch on (IG).
8. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B1780 is not output.

   HINT: 

   Codes other than DTC B1780 may be output at this time, but they are not related to this check.

NG → See step   7 

OK → See step   10 

1. Turn the power switch off.
2. Disconnect the cable from the negative (-) battery terminal.
3. Replace the front seat cushion spring assembly. Refer to DISASSEMBLY .

NEXT: Go to next step 

1. Connect the cable to the negative (-) battery terminal.
2. Connect the Techstream to the DLC3.
3. Turn the power switch on (IG).
4. Using the Techstream, perform Zero Point Calibration. Refer to INITIALIZATION .

   OK

   "Zero Point Calibration is complete." is displayed.

NEXT: Go to next step 

1. Using the Techstream, perform Sensitivity Check. Refer to INITIALIZATION .

   Standard

   27 to 33 kg (59.5 to 72.8 lb)

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